#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>


long long Fac(int N)
{
    if (N < 3)
        return 1;

    return Fac(N - 1) + Fac(N - 2);
}

int Fib(int n)
{
	int a = 1;
	int b = 1;
	int c = 1;
	while (n>2)
	{
		c = a + b;
		a = b;
		b = c;
		n--;
	}
	return c;
}



int main()
{
	int n = 0;
	scanf("%d", &n);
	int ret = Fib(n);
	printf("%d\n", ret);

	return 0;
}

